Electric space heater



ELECTRIC SPACE HEATER Filed Oct. 27, 1923 Fig. 1.

WITNESSES: lNVENTOR @mes C. Woodson.

Patented Dec. 15, 1925.

oFrIcE.

JAMES C. VIOODSON, OF EAST FITISBURG'I-I, PENNSYLVANIA, ASSIG-NOR TOWESTING- HOUSE ELECTRIC & .MANUFACTURING COMPANY, A CORPORATION OFPENNSYL- VAN IA.

ELE OTRIC SPACE HEATER.

Application filed October 27, 1923.

To all whom it may concern.-

Be it known that I, James C. lVooosoN, a citizen of the United States,and a resident of East Pittsburgh, in the county of Allegheny and Stateof Pennsylvania, have invented a new and useful Improvement in ElectricSpace Heaters, of which the following is a specification.

lily invention relates to electric heating means and particularly toelectric space heaters.

The object of my invention is to provide a multi-heat heating unitwherein the heat distribution laterally of th unit shall besubstantially the same for all conditions of operation.

In bread-baking ovens, it is highly desirable to employ heating elementsthat shall provide a substantially uniform distribution of heat over theoven surface available for baking processes under all conditions ofoperation, and the device embodying my invention is particularlyapplicable to such ovens wherein a plurality of heating units areenergized in various combinations thereof.

In practicing my invention, I provide a relatively narrow and elongatedresistorsupporting member upon which are mounted in spacedparallel-relation, three inclividual resistor members. The heatingcapacity of the intermediate resistor member is double that of either ofthe outer members. Suitable terminal means are provided for theindividual resistor members.

In the single sheet of drawings,

Figure 1 is a top plan view of av heating unit embodying my invention,

Fig. 2 is a view, in side elevation thereof,

Fig. 3 is a view in end elevation thereof, and

Fig. 1 is a vertical view, in lateral section, of a modified form ofterminal construction.

A heating unit 11 comprises a relatively narrow and elongated planeresistor-supporting plate or bar 12, of a suitable electrio-insulatingmaterial, such as asbestos lumber. A plurality of individual resistormembers 13, 14 and 15 are located in parallel-spaced relation on theplat 12 and extend longitudinally thereof, the distance therebetweenbeing preferably substantially the same as the distance from the outerSerial No. 671,173.

resistor members to the edge of the plate. The resistance of each of theresistor members 13 and 15 is substantially twice that of the resistormember 14, whereby the latter resistor member has twice the heatingcapacity of each of the outer resistor members.

The resistor members 13, 1 1 and 15 are in the shape of helically woundWire and I prefer to employ a helix of relatively large. diameter ascompared to the lateral width of the plate 12, for a purpose to behereinafter described in detail.

Any suitable or desired means for securing the resistor members againstthe surface of the plate 12 may be employed and I have illustrated aplurality of metal members 16, of hair pin shape, the loop ends of whichoperatively engage the wire of the resistor members and which extendthrough suitable openings provided in the plate- 12 and have their outerends bent over against the other surface thereof, substantially asillustrated in Fig. 2 of the drawing.

A plurality of terminal members is provided for each of the resistormembers and I have illustrated a machine screw 17 that extends throughsuitable openings in the plate 12. As the members 16 are in directoperative engagement with the resistor member, I prefer to employ asecond plate 18 of asbestos lumber coextensive with and located closelyadjacent to the plate 12. The screws 17 are made long enough to extendthrough the plate 18 and nuts 19 are located thereon in order to holdthe two plates in close operative engagement. Any suitable or desiredconstruction to permit of con necting the supply circuit conductors (notshown) to the terminal members may be provided, and as this forms nopart of my invention, I have not deemed it advisable to furtherillustrate this.

Means for permitting of securing the heating unit 11 in its properoperative position within an oven structure may comprise a plurality ofopenings 21 adjacent to each end to permit of extending therethroughsuitable machine screws (not shown).

If it it necessary that there be no live parts on the under side of theheating unit 11, I may employ the terminal construction illustrated inFig. 4, in which a flathead machine screw 22 extends through the twoplates 12 and 18, the head of the screw being countersunk 1n the plate18 and a mass 23 of a suitable electric-insulating cement, beingemployed to cover the head.

The heating unit hereinbefore described is intended to be employed inconnection with a multi-heat switch that is adapted to connect theplurality of resistor members in series or in series-parallel relationrelatively to each other.

These connections give what are usually termed low, intermediate, andhigh heat, when it is desired to obtain a low heat, resistor members 13and 15 are connected in parallel-circuit relation relatively to eachother and in series circuit relation relatively to resistor member 14.The value of the current traversing resistor members 13 and 15respectively, is substantially one-half that traversing resistor member14, and the heat distribution laterally of the heating unit will be suchthat a maximum value is obtained substantially over the intermediateheating unit 14.

The temperature of the heating units 13 and 15 will be somewhat lowerand it will drop still further toward the edge of the unit when it isemployed as a single heating unit,

When it is desired to obtain a medium or intermediate heat, we mayenergize either the intermediate,resistor 14, or only the two outerresistors 13 and 15 which are then connected in parallel-circuitrelation relatively to each other. In either case, we will obtain asubstantially uniform distribution of heat laterally of the plate of theheating unit and if only the intermediate resistor let is energized, thetemperature is maximum at or above the intermediate portion of theheating unit.

If the two outer resistor members are energized, the temperature will belower over the intermediate portion, but the temperature over each ofthe outer heating units will be substantially the same and drop butlittle intermediate thereof laterally of the heating unit.

When it is desired to obtain a high heat, all three resistors areconnected in parallelcircuit relation relatively to each other and asthe resistance of the intermediate member is less than that of either ofthe outside members, a larger current will traverse the intermediateresistor and the temperature over this resistor will be higher than thetemperature over either of the outer resistors but, again, asubstantially symmetrical distribution of temperature laterally of theheating unit is obtained.

It is evident that when a single heating unit is employed, thetemperature at the edges of the heating unit will be lower than over anyportion intermediate thereof. However, when a plurality of such heatingunits are placed in side-by-side relation, the temperature over the sideedges of the heat ing units will not be materially lower than verintermediate portions, by reason of the fact that heat radiation fromthe sides of the individual heating units is substantially prevented.

It is highly desirable, where large numbers of pans of dough are placedin the baking chamber of a bread baking oven, that the heat generationbe such, whether low, intermediate, or high heats are employed, that theheat. curve laterally of the individual heating units be not materiallyshifted, as this would result in uneven baking of the bread. Such acondition exists when only two individual resistor members are employedper heating unit, as only one of these is energized in the intermediateheating condition and. it is evident that when only one resistor isenergized, the heat distribution laterally of such a heating unit isvery different than that which obtains in the low and the high heatconditions of operation when both resistor members are energized.

Various modifications and changes may be made herein without departingfrom the spirit and scope of the invention, and I desire therefore, thatonly such limitations shall be placed thereon as are imposed by theprior art or are set forth in the appended claims.

I claim as my invention:

1. A heatin unit comprising an elongated, relative y narrow, planesupporting member, and a plurality of spaced and parallel-extendingresistormembers mounted on one surface of said supporting member, one ofsaid resistor members having a heat capacity equal to that of the otherresistors combined.

2. A heating unit comprising an elongated relatively narrow, planesupporting member, and a plurality of spaced and parallel-extendingresistor members mounted on one surface of said supporting member, theintermediate resistor member having a heating capacity equal to that ofthe other resister members combined.

3. A heating unit comprising an elongated, relatively narrow, 3121116supporting nember, and a plurality of spaced and parallel-extendingresistor members mounted on one surface of said supporting member, andadapted to be connected in various combinations relatively to eachother, the resistance of the outer resistor members being less than thatof the intermediate resistor member whereby substantially similar heatdistributien is'etlected laterally of the supporting member in thevarious connections.

In testimony whereof, I have hereunto subscribed my name this 20th dayof October 1923.

JAMES C. lVOODSON.

